Fig. 1.

Symptoms after each challenge infection. The symptoms recorded in the diary cards were graded by severity (1, 2 or 3) and a total severity score from all symptoms calculated by adding all the scores recorded by all subjects on each day over the first 28 days after the first and third challenges, and 21 days after the second challenge (as the third challenge was brought forward to 21 days after the second). The aggregate score is the sum of all daily scores after each challenge. Score is higher after the first does, indicating activation of innate immunity, but decreases after following doses.